Optical navigation module is an essential component of consumer electronics requiring user input through a GUI (Graphical User Interface). As illustrated in FIG. 7, the typical key building blocks of an optical navigation module are a light sensor 701, a light source 703, a light shield 705 disposed around the light sensor 701, an optical element 707 and a substrate 709 for mounting all the above elements. In a conventional design, the plane 710 defined by the substrate, the light source emission surface and the light sensor sensing surface is always facing or in parallel with the tracking surface 711 of the module, which imposes a limit on the thickness of the optical navigation module and in turn a limit on the application of the optical navigation module.